Magnetic transducer assembly with nonmagnetic core-holding inserts



Dec. 16. 1969 E.-K RO'NFELD ET AL "3.

MAGNETIC TRANSDUCER ASSEMBLY WITH N'QNMAGNETIC LEONA/w E, KEONFELDGORE-HOLDING INSERTS Filed Nov. 22, 1967 m T N E V m JQHN W. HOGAN FE.&

United States Patent 3,484,565 MAGNETIC TRANSDUCER ASSEMBLY WITH N 0N-MAGNETIC CORE-HOLDING INSERTS Leonard E. Kronfeld and John W. Hogan,Minneapolis,

Minn., assignors to The Nortronics Company, Inc., Minneapolis, Minn., acorporation of Minnesota Filed Nov. 22, 1967, Ser. No. 685,112 Int. Cl.Gllb 5/10 U.S. Cl. 179-1002 5 Claims ABSTRACT OF THE DISCLOSURE A coreholder for use in a magnetic transducer including a housing member andan insert fixedly positioned therein for receiving at least a portion ofthe core and maintaining said core fixedly positioned relative to thehousing member. The insert is constructed with a portion thereofoperating in a spring-like fashion to automatically position the core,along at least one major axis of the core with respect to the housingmember.

BACKGROUND OF THE INVENTION Field of the invention This inventionpertains to a new and improved magnetic transducer and more particularlyto an improved core holder for use in magnetic transducer constructions.

In the magnetic transducer industry, devices referred to as core holdersare utilized to maintain the magnetic cores of the transducers in adesired position during assembly, which core holders are normallyintegrated into the finished transducer. The core holders areconstructed in a variety of forms. In general, they are hollow, somewhatrectangularly shaped structures adapted to mate with other core holdersto form an enclosure. The side of a core holder which adjoins a matingcore holder is open to form a core and winding receiving cavity withinthe enclosure.

Each of the core holders contains at least one generally U-shaped corepiece. The core pieces are fixedly positioned in the associated coreholder so that the tips, which are the extreme flat surfaces at the endsof the core pieces that cooperate with a second core piece to form frontand real magnetic flux gaps, extend outwardly into the open side of thecore holder. The core tips are lapped, generally utilizing certain padsor portions of the open side of the core holder as a reference, to placethe tips as closely in a plane as possible. In some instances themanufacturer attempts to place the core tips and the pads in a commonplane and in some instances the core tips are in a plane spaced from aplane through the pads; however, this is not critical to the presentinvention and will not be elaborated upon further.

The assembled core holder and associated core pieces make up a bodysection that is usually described as a half section. Prior to assemblyof the body sections, electrical windings are positioned around portionsof the cores. When the body sections are joined to form a transducer,the enclosure formed by the core holders is generally open at the rearand receives a terminal board therein having the electrical connectionfor the windings thereon. A flux gap is formed between the front coretips of mating core pieces in a transducer, the dimensions of which arecritical to the magnetic characteristics thereof. The relative positionsof the rear core tips are generally important also; however, themagnetic flux gap between the front core tips is the gap usuallyutilized for tape contact and, therefore, to simplify this disclosurethe front core tips will be referred to simply as core tips with theunderstanding that the rear core tips are included where appropriate.

ice

Description of the prior art In the prior art, core holders aregenerally formed by casting, molding, or machining a nonmagneticmaterial into the desired shape. The core holder has a cavity thereinwith a slot-like depression formed in the inner surface of the lowerwall and a mating slot formed in the front wall. The depression in thelower wall and the mating slot in the front wall generally form acontinuous groove adapted to receive a core piece therein. The cavity inthe core holder is large enough so that an electrical winding can bepositioned over the core piece therein. In this prior art a completelynew core holder must be designed each time a variation, such asadditional tracks, etc. is incorporated into the transducer. Thus,separate dies, molds, or the like must be utilized to produce eachvariation of transducer.

SUMMARY OF THE INVENTION In the present transducer a core holder isutilized which includes a housing member and insert fitted therein. Thehousing member, which may be a standard housing memher that is utilizedin a large series or variety of core holders, may be produced in avariety of ways, such as extruding, stamping, etc.; and because it hasvery little or no details formed on the inner surface of the walls, itmay be produced in a manner which is simpler and less expensive thanmolding or casting. In the embodiment which will be described in thefollowing specification, the housing is stamped and formed from a flatpiece of material into the desired shape; however, it should beunderstood that a variety of other methods might be utilized to producethe housing which would still be within the scope of this invention. Ingeneral the housing is constructed of a non-magnetic material which hasthe proper workability so that the housing member can easily :be formedtherefrom, but which has sufficient hardness and strength so that lateroperations, such as grinding and lapping, can be performed.

An insert, which is constructed from a non-magnetic material, such asplastic or the like, having a desired amount of resiliency is designedto fit within the housing and provide all of the inner details for thecore holder. The insert in the first embodiment to be described, isproduced from a fiat piece of material which is stamped and formed intothe desired shape. Core piece receiving channels are formed within thecore holder by the insert; and a portion of the insert in juxtapositionto each channel provides spring bias on the core piece inserted therein.The spring bias on the core piece tends to correctly position andmaintain the core piece within the channel. To produce variations incore holders a variety of inserts are produced which contain the desiredvariations in detail, such as different numbers of core piece receivingchannels.

With respect to any particular transducer, openings or slots are formedin the front wall of the housing member to correspond to the number ofchannels desired. An insert, chosen from a variety of available inserts,having the desired number of core piece receiving channels is fixedlypositioned within the housing member. The housing member and the variousinserts each have means associated therewith which cooperate tocorrectly position the insert within the housing member. The portion ofthe insert acting as a spring correctly positions the core piece withinthe core holder in a transverse direction and the assembler positionsthe core piece along the channel in the insert to correctly position thecore piece axially.

Thus, in the present device a standard housing member is utilized withany one of a variety of inserts to produce a great variety of coreholders. Because a standard housing member is utilized to receive theinsert, the cost of the core holder is greatly reduced. Also, becausemethods such as stamping or the like may be utilized to produce thehousing members and the inserts, the cost of production of the coreholders is greatly reduced while the speed or amount of production isgreatly increased. Also, because spring means are incorporated withinthe insert to correctly position and hold the core pieces therein,assembly time of the transducers is greatly reduced.

It is an object of this invention to provide a new and improvedtransducer.

It is a further object of this invention to provide a standard housingmember which is adapted to receive any of a variety of inserts thereinto produce a great variety of core holders.

It is a further object of this invention to provide a core holder whichis relatively inexpensive and simple to produce.

It is a further object of this invention to provide an insert and ahousing member which cooperate to produce a core holder that aids incorrectly positioning and that will hold the core pieces placed therein.

These and other objects of this invention will become apparent to thoseskilled in the art upon consideration of the accompanying specification,claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Referring to the drawings, whereinlike characters indicate like parts throughout the figures:

FIGURE 1 is a view in perspective of a housing member;

FIGURE 2 is a view in perspective of an insert;

FIGURE 3 is a view in top plan of the insert illustrated in FIGURE 2;

FIGURE 4 is a view in top plan of the core holder, including the insertillustrated in FIGURE 2 positioned in the housing illustrated in FIGURE1, illustrating core pieces inserted therein;

FIGURE 5 is a view in side elevation of the core holder illustrated inFIGURE 4, parts thereof broken away and shown in section;

FIGURE 6 is a view in side elevation of a somewhat different embodimentof a core holder;

FIGURE 7 is a detailed view of a corner of the embodiment of the coreholder illustrated in FIGURE 6;

FIGURE 8 is a view in perspective of another embodiment of an insert;and

FIGURE 9 is a diminutive view in perspective of an assembled pair ofcore holders.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGURE 1 illustrates a housingmember generally designated 10 having side walls 11 and 12, a front wall13 and a lower wall 14. The housing member 10 is adapted to mate withanother housing member 10 to form a generally box-shaped enclosure asshown in FIGURE 9.

The side wall 11 has a front and a rear portion 18 and 19 and the sidewall 12 has a front and a rear portion 20 and 21 respectively. The rearportions 19 and 21 are laterally offset from the front portions 18 and20 to form a discontinuity or steps 22 and 23 in each of the side walls11 and 12. As specifically shown, each step extends the entire width ofits associated side wall and is located at approximately thelongitudinal center thereof. It should be understood, however, that adiscontinuity in the side walls 11 and 12 could be embodied in manyforms other than by steps 22 and 23 as specifically shown; and it isintended that the term discontinuity, as used herein, includes all formsof structure which would perform the functions to be explainedpresently.

In the present and preferred embodiment of the invention, the housingmember 10 is made from a fiat blank of nonmagnetic metallic material,such as brass, and stamped and formed for a dual-track transducer. Apair of core piece receiving openings 25 and 26 are formed in the frontwall 13. The openings 25 and 26 are substantially rectangular in shapeand in the present embodiment are formed by shearing the material fromthe upper edge of the front surface 13 downwardly and forcing thematerial outwardly to form outwardly extending lips 27 and 28,respectively. It should be understood that the material in the openings25 and 26 could be removed completely, but the lips 27 and 28 are formedin the present embodiment for the purposes which will be explainedpresently. A pair of inwardly extending disk-shaped extrusions 29 and 30are formed on the inner surface of the lower wall 14 in a spaced apartrelationship adjacent the rear edge of the lower wall 14. An axiallyextending slot 31 is formed in the lower wall 14 and is adapted toreceive a magnetic shield therein. Adjacent the rear end of each of theside walls 11 and 12 is a rectangularly shaped notch 32 and 33,respectively. The notches 32 and 33 when joined with similar notches inthe opposite mating housing form rectangular shaped openings adapted toreceive the ends of a terminal board, not shown, therein. The terminalboard contains the electrical connections of the winding in the finishedtransducer.

Although a dual-track or binaural transducers are illustrated in thedrawings, it should be understood that the housing member 10 can beadapted for use in different types of transducers. If a monaural orsingle-track trans ducer is desired, a single core piece receivingopening is formed in the front wall 13. Also, if more than two tracksare desired more than two core pieces receiving openings are formed inthe front wall 13. In each em bodiment, the position of the opening inthe front wall 13 must conform to the desired position of the frontedges of the core tips in the core holders. The position of the openingsin the front wall 13 of the housing member 10 will be described in moredetail presently.

FIGURES Z and 3 illustrate one form of insert generally designated 35which is adapted to fit within the housing 10. The insert 35 isgenerally rectangular in shape and may be stamped or otherwise formed ofmaterial having the desired resiliency. While it should be understoodthat insert 35 can be made from any material, preferably non-magnetic,having the desired resiliency and thickness, such as plastic, metal,etc., in the present embodiment, insert 35 is made relatively thin, andtherefore, is constructed from a beryllium copper alloy. Also, a numberof variations may be incorporated in the insert 3.5 to produce differenttypes of transducers, such as monaural, binaural, etc. The proper typeof insert 35 is incorporated in a housing member 10- having the desirednumber of openings in the front wall thereof to produce monaural,binaural, etc., core holders. For example, in the present embodiment,housing 10 is formed for a binaural head, thus insert 35 is shown to befor a binaural or two-track head.

The front edge of the insert 35 is designated 36, the rear edge isdesignated 37, one side is designated 38 and the other side isdesignated 39. The sides 38 and 39 of the insert 35 are separated intofront portions 40 and 42 and rear portions 41 and 43. The rear portions41 and 43 are laterally outwardly ofiset at 44 and 45 from the frontportions 40 and 42. The offset distance is not critical but should besufficient to allow the front edges of the rear portions 41 and 43 ofthe insert 35 to butt against the rear edges of the front portions 18and 20 of the housing member 10 when the insert is correctly positionedtherein. The offsets at 44 and 45 in the insert 35 are positionedrearwardly from the front edge 36 a distance such that when positioningthe insert 35 front to back within the housing member 10, the frontedges of the rear portions 41 and 43 of the insert 35 will abut the rearedges of the front portions 18 and 20 of the housing member 10,indicated as steps 22 and 23, respectively, without front edge 36engaging front wall 13.

The insert 35 is retained in the correct position within the housingmember during assembly of the core holder by the following means. Thedistance between the outer surfaces of the rear portions 41 and 43 ofthe insert 35 is slightly greater than the distance between the innersurfaces of the rear portions 19 and 21 of the housing member 10. Wheninsert 35 is positioned within the housing member 10 the rear portions41 and 43 of the insert 35 are forced inwardly by the rear portions 19and 21 of the housing member 10. Since the entire insert 35 isconstructed of a resilient material the rear portions 41 and 43 thereofproduce substantially equal forces outwardly on the rear portions 19 and21 of the housing member 10. Thus, the rear portions 41 and 43 of theinsert 35 act as springs to position the insert 35 correctly within thehousing member 10 from side-to-side or in a lateral or transversedirection.

The insert 35 has a pair of circular openings 46 and 47 which arepositioned adjacent the rear edge 37 thereof and have a diametersomewhat larger than the extruded portions 29 and 30 of the housingmember 10. When the insert 35 is placed in the housing member 10 so thatthe front edges of the rear portions 41 and 43 of the insert 35 areabutting the rear edges of the front portions 18 and of the housingmember 10, the openings 46 and 47 are generally coaxial with theextruded portions 29 and of the housing member 10. The offsets at 44 and45 in the insert and the discontinuities 22 and 23 in the housing member10, are utilized to correctly position the insert 35 front to backwithin the housing member 10, and the spring-like rear portions 41 and43 of the sides 38 and 39 correctly position the insert 35 transverselywithin the housing member 10. When the insert 35 is correctly positionedwithin the housing member 10 the extruded portions 29 and 30 extendslightly above the insert 35 through the openings 46 and 47. The insert35 is fixedly engaged within the housing member 10 by riveting the partof the extruded portions 29 and 30 extending through the openings 46 and47 in the insert 35.

The insert 35 has a pair of slots 50 and 51 formed therein which extendfrom the front edge 36 rearwardly and angle obliquely toward the sides38 and 39, respectively. Front and rear upstanding flanges 52 and 53 arespaced apart along the inner edge of slot 50 and are formed by turning aportion of the material from the slot 50 upwardly. In a similar fashion,front and rear upstanding flanges 54 and 55 are formed and spaced apartalong the inner edge of slot 51. A single upstanding flange is formed,in a manner similar to the flanges 52-55, at the outer edge of each ofthe slots 50 and 51; and these two flanges are designated 56 and 57respectively. The flanges 56 and 57 each have integral therewith anadditional portion of material designated 58 and 59, respectively, whichportions extend forwardly and slightly inwardly to partially overlie theslots 50 and 51. More particularly, portion 58 is integral with flange56 and overlies a portion of slot 50; and portion 59 is integral withflange 57 and overlies a portion of slot 51. The additional portions ofmaterial 58 and 59 provide a force inwardly generally perpendicular tothe axial length of the slots 50 and 51 when said portions are flexedoutwardly; and they will be referred to as spring means 58 and 59 in theremainder of this specification. The slots 50 and 51 in the insert 35cooperate with the housing member 10 to form core piece receivingchannels. It should be understood that the core piece receiving channelscan be formed in a variety of ways and shapes; and the term channel isused broadly in this specification to means that area defined by theinsert or by the insert and housing which is adapted to receive a corepiece therein.

In FIGURE 3, the position of a core piece 60 is illustrated in dottedlines in the slot 51 to show the approximate relationship of the variousflanges 54, 55 and 57. The distance between the two flanges 54 and 55 onone side of the slot 51 and the single flange 57 on the opposite side ofthe slot 51 is slightly greater than the width of the core piece 60. Thedistance between the two flanges 54 and 55 on one side and theforwardmost core engaging portion of the spring means 59 on the oppositeside is somewhat less than the width of the core piece 60 so that thespring means 59 must be flexed outwardly to place the core piece 60 inthe slot 51; and spring means 59 urges the core piece 60 into thecorrect transverse position in the slot 51.

A centrally located slot 65 having a pair of upstanding flanges 66 onone side thereof and a single upstanding flange 67 on the opposite sideextends axially between the slots 50 and 51. The two flanges 66 and theopposite flange 67 are formed by turning a portion of the material fromthe slot 65 upwardly. The slot 65 is aligned with the slot 31 in thehousing member 10 when the insert 35 is correctly positioned therein andis adapted to receive a piece of magnetic shielding material therein toprevent cross-talk or magnetic interaction between the two tracks.

When the insert 35 is correctly positioned within the housing member 10and fixedly engaged therein, the entire assembly constitutes a coreholder generally designated 70 in FIGURES 4 and 5. Core holder 70 isillustrated in FIGURES 4 and 5 with the core piece 60 in the slot 51,and a second core piece 71 engages in the slot 50. When the core piecesare fixed in position in the core holder, it makes a transducer bodysection described as a half-section. When the core piece 60 is correctlypositioned in the slot 51, the spring means 59 urges the core piece 60into abutment with the rearmost flange 55 and an edge of the opening 26.In a similar fashion the spring means 58 urges the core piece 71 intoabutment with the rearmost flange 53 and an edge 74 of the opening 25.Neither of the core pieces 71 or 60 rest against the forwardmost flanges52 and 54 of the insert 35 since the inner edges 74 and 75 of theopenings 25 and 26 are utilized as reference edges in the correctpositioning of the core pieces.

To insure that the rearmost flanges 53 and 55 and the edges 74 and 75will always operate to position the core pieces 71 and 60, front flange52 is slightly removed or laterally offset from the plane defined by theside of flange 53 which engages core piece 71 and edge 74 and,similarly, front flange 54 is laterally olfset from the plane defined byflange 55 and front edge 75. This offset must be at least equal to themaximum allowable transverse variation or tolerance in the position ofthe core pieces 60 and 71, also bearing in mind the tolerances in thefront slots 25 and 26, so that in the worst allowable cases the adjacentsurface of the core pieces 71 or 60 would just contact its associatedfront flange 52 or 54, respectively. In spite of this oflFset, frontflanges 52 and 54 function to aid in the positioning of said core pieces71 and 60.

An upstanding flange 76 and 77 is illustrated at the rearmost ends ofthe slots 50 and 51. These flanges 76 and 77 are utilized in the furtherassembly of the transducer and do not form a part of the presentinvention. In general, the core pieces 71 and 60 will not contact theflanges 76 and 77, however, in some special cases they may.

The core pieces 71 and 60 are correctly positioned in the slots 50 and51 in a transverse direction by the action of the spring means 58 and 59of the insert 35. The core pieces 71 and 60 are then positioned, frontto back, until the front edges of the tips thereof extend through theopenings 25 and 26 in the front wall 13 of the housing member 10 theproper distance. This proper positioning may be accomplished eithermanually or automatically through the use of proper fixtures and thelike; and as means for accomplishing this are well known in the magneticart, it need not be discussed further.

A plane extending through steps 22 and 23 is a reference plane for thefront to back adjustment of the core pieces. This plane is shown bydotted lines in FIG. 4, and

is indicated by the numeral 81. Core pieces 71 and 60 are positioneddownwardly to butt against a reference portion of housing member 10 toprovide the up and down position of the front tips of core pieces 71 and60. This reference can be either the top surfaces of lips 27 and 28 orthe inside surface of wall 14. In constructions which do not utilizelips 25 and 26, the inner horizontal edge of housing 10 defining thedepth of openings 25 and 26 might be used as a reference. It might alsobe mentioned that the inside surface of front wall 13 has been used inthe past as a reference for the front to back adjustment; and if desiredto do so, it may still be utilized in the present invention by movingthe core pieces forwardly until they butt against such surface. It mightbe mentioned in connection with the preferred embodiments of theinvention shown that it is a distinct advantage to utilize steps 22 and23 on the reference plane for the front to back adjustment as previouslydescribed and with such steps 22 and 23 also functioning as referencesurfaces for the spring clips as described in .copending application(see page 16).

Thus, the form of core holder 70 as shown brings together in a desirableand improved cooperative relationship the development of the springclips as described in said copending application, Ser. No. 580,091, andits development of the preferred form of tthe instant invention.

The necessary accurate positioning of core pieces is known in themagnetic art and various reference surfaces and edges have been used.Without going into this in any further detail, three significant aspectsof the invention in this respect might be mentioned at this point.First, the invention provides for the lateral or side-to-side adjustmentof the core piece; second, spring means 58 and 59 hold the core piece inposition to be further adjusted, front to back, etc.; and then, theymaintain the proper position of the core pieces until the core piecesare suitably bonded or afiixed to the core holder. Also, the inventionprovides for an available reference plane in steps 22 and 23 for thefront to back adjustment of the core pieces.

After the core pieces 60 and 71 are positioned in the core holder 70,they are fixedly engaged therein by suitable means such as applyingepoxy or other suitable adhesive material thereto. The front tips 72 and73 and the back tips of the core pieces 71 and 60 are then lapped toform a smooth uniform plane surface, which when joined with the tips ofcore pieces in a mating core holder with a suitable gap spacer, betweenthe front tips of mating half sections, of foil or otherwise, will forma uniform accurate fiux gap, In general, the upmr surfaces 15, 16 and 17of the side walls 11 and 12 and the front wall 13, respectively, areutilized as reference surfaces during the lapping to insure that thefront tips 72 and 73 and the back tips of the core pieces lie in adesired plane, which will be parallel with the plane containing the tipsof the core pieces in the mating core holder. The lapping produces apressure on the front wall 13 which might tend to move or bend the frontwall 13 relative to the remainder of the core holder. To prevent suchmovement of the front wall 13, each of the corners between the sidewalls 11 and 12, and the front wall 13, are reinforced at 78 and 79. Inthis embodiment the reinforcement at 78 and 79 is a continuous portionintegral with the side walls 11 and 12, and the front wall 13, whichportion is formed into corners during the stamping and bending of tthehousing member 10.

With the core pieces 71 and 60 fixedly engaged in the core holder 70,and the tips 72 and 73 properly lapped, a mating core holder is joinedtherewith to form a generally box-like hollow structure or enclosure 80,illustrated in FIGURE 9. The illustration of the box-like structure 80in FIGURE 9 does not illustrate a method of attaching the two co reholders 70 together, since there are several means for this purpose.Preferably, however,

the two core holders are attached by the spring clips described in thepreviously mentioned copending application entitled Improved MagneticTransducer, Ser. No. 580,981, filed Sept. 21, 1966 and which need not befurther described herewith. While the structure might be utilized as atransducer in the form illustrated in FIG- URE 9, once assembled itgenerally is placed within a case, not shown, having a similar shape butsomewhat larger dimensions. The case is constructed of a material whichshields the transducer from stray magnetic flux as well as other harmfuleffects. The case has a pair of openings in the front thereof to receivethe front edge of the tips 72 and 73 of the core pieces 71 and 60therethrough. In the assembly of the structure 80 within the case, it isimportant that the core pieces 60 and 71 do not touch the sides of thecase.

As shown in FIG, 4, portions of lips 27 and 28, indicated by thenumerals 82 and 83, extend laterally outwardly beyond the adjacent edgesof the core pieces 71 and 60. Edges 82 and 83 can be used as referenceedges abutting the adjacent sides of the case openings, not shown, tomaintain a controlled spacing between the core pieces and a case laterassembled around the housing.

A differene embodiment of the reinforced corners of the housing member10 is illustrated in FIGURES 6 and 7, wherein components similar tothose in the first embodiment are designated with similar numeralshaving a prime added. In this embodiment, the front wall 13' and theside walls 11 and 12 are stamped from a flat piece of material and arean integral part of the lower wall 14'. The front wall 13 has a pair oftabs 96 and 91 extending outwardly from either end thereof. To form thehousing member 10 the side walls 11 and 12 are bent upwardly at an angleof approximately with the lower wall 14', and the front wall 13 bentupwardly at an angle less than 90. The tabs 90 and 91 are bentrearwardly at an angle of approximately 90 to the front wall 13 injuxtaposition with portions of the side Walls 11' and 12' respectively.The tabs 90 and 91 are fixedly attached to the side walls 11' and 12 bysome means such as brazing, welding, riveting, etc., and reinforce thefront wall 13' so that it does not move during subsequent assemblyoperations, such as lapping and polishing of the core tips and/ or theupper surface 17 thereof.

FIGURE 8 shows a different embodiment of the insert for use in housing10. This insert of FIGURE 8 is designated generally by the number 35;and its components similar to insert 35 are designated with similarnumerals having a prime added. Insert 35 is nonmagnetic and is formed ofa molded plastic. Rear lateral edges 41' and 43' extend laterallyoutwardly beyond front lateral edges 40' and 42' to provide shoulders orabutment portions 44 and 45'. Shoulders 44' and 45 abut the rear edgesof the front portions 18 and 20 of housing member 10, which rear edgesare the steps 22 and 23, to position the insert in housing 10 in a frontto back relationship. Edges 41' and 43' in juxtaposition with rearportions 19 and 20 position insert 35 in the proper sideto-siderelationship with housing member 10. Insert 35' is fixed to housingmember 10 by a suitable adhesive. Slots 50' and 51' form core piecereceiving channels. Resilient arms 58' and 59 form spring means, eachalong one side of a different one of the channels 50' and 51. Theopposite channel forming walls are designated by the numerals 92 and 93respectively; and each wall is divided into a front portion and a rearportion. The rear portion of wall 92 is designated by the numeral 53 andthe front portion by the numeral 52 The rear portion of wall 93 isdesignated by the numeral 55' and the front portion by the numeral 54'.A core piece or, if laminated, core pieces, received into channel 50will flex the resilient arm 58 laterally outwardly; and arm 58 willengage and bias the said core piece toward and into engagement with rearwall portion 53. Similarly, a core piece received into channel 51 willflex the resilient arm 59 laterally outwardly; and arm 59 will engageand bias the said core piece toward and into engagement with rear wallportion 55. In a core holder assembly, shown in FIG. 4 with respect toinsert 35, front Wall portions 52 and 54 preferably will not engage butwill be closely adjacent the core pieces received into their respectivechannels 50' and 51' and, wherein the core pieces will be biased oneagainst edge 74 and rear wall portion 53' and the other against edge 75and rear wall portion 55'.

In view of the more complete explanation of insert 35 and the similaritybetween insert 35 and 35', further description of insert 35 is believedto be obvious. It might be mentioned, however, that insert 35' is formedwith a shield receiving slot 94.

Thus, an improved magnetic transducer comprised of mating core holders,each including a housing member and an insert, has been disclosed. Thehousing member can be made in a standard form, and a variety of singleand multi-track transducers can be produced by utilizing inserts whichvary slightly from the one disclosed. Because of this adaptability andbecause of the simplicity of the housing members and the inserts, themanufacturing cost per unit is minimized. Also, the insert holds andpositions the core pieces within the core holder, thus reducing assemblytime and the number of operations.

While we have shown and described specific embodiments of thisinvention, we desire it to be understood that this invention is intendedto be defined and covered solely by the appended claims.

What is claimed is:

1. A magnetic transducer comprising:

(a) a plurality of housing members cooperating with each other to forman enclosure;

(b) non-magnetic insert means fixedly positioned in said housingmembers, said insert means having at least one core piece receivingchannel formed therein with a portion of said insert means formingspring means adjacent said channel; and

(c) magnetic core means positioned in said channel and maintained in adesired position by said spring means.

2. A magnetic transducer as set forth in claim 1 wherein each of saidhousing members is formed from a stamped metal blank of non-magneticmaterial.

3. A magnetic transducer as set forth in claim 1 wherein a portion of anedge of said channel defined by said insert means cooperates with aportion of the housing member to form a reference plane for positioningsaid magnetic core means in said housing; and said spring means ispositioned opposite said reference plane and urges said core means intoposition against said portions defining said reference plane.

4. Dual channel magnetic transducer comprising:

(a) two housing members cooperating with each other to form anenclosure;

(b) an insert fixedly positioned in each of said housing members, eachof said inserts having two channels formed therein with portions of saidinserts forming spring means adjacent each of said channels;

(c) two magnetic cores each including two U-shaped core pieces; and

((1) each of said core pieces being positioned in one of said channelsand maintained in a desired position by said spring means so as to formtwo magnetic cores each having at least one useful flux gap therein.

5. A core holder for a magnetic transducer, comprising:

(a) a housing member adapted to be joined with a like housing member toform a box-like enclosure;

(b) a non-magnetic core piece supporting insert fixedly attached to saidhousing member;

(c) said insert having a core piece receiving slot therein;

(d) a portion of said insert forming fiange means along one edge of saidslot; and

(e) a portion of said insert forming spring means along an edge of saidslot opposite said flange means to bias a core piece mounted in saidslot against said flange means to position the core piece in the coreholder.

References Cited UNITED STATES PATENTS 3,171,903 3/1965 Wheeler et al.179-1002 3,330,666 7/1967 Studley et al. 179-1002 3,340,518 9/1967Hanson 179-1002 3,348,301 10/1967 Schulte 179-1002 3,357,097 12/1967Schulte 179-1002 3,358,275 12/1967 Schulte 179-1002 3,359,629 12/1967Smith 179-1002 3,394,362 7/1968 Gooch 179-1002 3,412,216 11/1968 Rosadoet al 179-1002 BERNARD KONICK, Primary Examiner JEROME P. MULLINS,Assistant Examiner US. Cl. X.R.

